Empower your environment with intelligent illumination using BH1680FVC and STM32F303RC

Beyond brightness: Exploring the world of ambient light sensing

Published Sep 24, 2023

Click board™

Ambient 18 Click

Dev. board

Fusion for ARM v8

Compiler

NECTO Studio

MCU

STM32F303RC

Unleash the potential of your smart devices with our ambient light sensing solution – it's the gateway to a brighter, more efficient future

Hardware Overview

How does it work?

Ambient 18 Click is based on the BH1680FVC, an analog current-output ambient light sensor from Rohm Semiconductor. It comprises photodiodes, amplifiers, and current mirror circuits and can detect a wide range of illuminance up to 10klx, providing excellent responsivity close to the human eyes' response. It has stable performance over a wide temperature and voltage range and a built-in shutdown function. It is characterized by good output linearity across a wide illumination range and low sensitivity variation across various light sources suitable to sense the amount of the present ambient light. It also has four configurable modes of operation and a shutdown mode associated with three gain modes: high-gain

mode, medium-gain mode, and low-gain mode. The desired gain mode is selected through CS and PWM pins of the mikroBUS™ socket labeled GC1 and GC2. The output of the BH1680FVC can be converted to a digital value using MCP3221, a successive approximation A/D converter with a 12-bit resolution from Microchip, using a 2-wire I2C compatible interface, or can be sent directly to an analog pin of the mikroBUS™ socket labeled as AN. Selection can be performed by onboard SMD jumper labeled ADC SEL to an appropriate position marked as AN and I2C. The MCP3221 provides one single-ended input with low power consumption, a low maximum conversion current, and a Standby current of 250μA and 1μA,

respectively. Data can be transferred at up to 100kbit/s in the Standard and 400kbit/s in the Fast Mode. Also, maximum sample rates of 22.3kSPS with the MCP3221 are possible in a Continuous-Conversion Mode with a clock rate of 400kHz. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the VIO SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.

Features overview

Development board

Fusion for ARM v8 is a development board specially designed for the needs of rapid development of embedded applications. It supports a wide range of microcontrollers, such as different ARM® Cortex®-M based MCUs regardless of their number of pins, and a broad set of unique functions, such as the first-ever embedded debugger/programmer over WiFi. The development board is well organized and designed so that the end-user has all the necessary elements, such as switches, buttons, indicators, connectors, and others, in one place. Thanks to innovative manufacturing technology, Fusion for ARM v8 provides a fluid and immersive working experience, allowing access anywhere and under any

circumstances at any time. Each part of the Fusion for ARM v8 development board contains the components necessary for the most efficient operation of the same board. An advanced integrated CODEGRIP programmer/debugger module offers many valuable programming/debugging options, including support for JTAG, SWD, and SWO Trace (Single Wire Output)), and seamless integration with the Mikroe software environment. Besides, it also includes a clean and regulated power supply module for the development board. It can use a wide range of external power sources, including a battery, an external 12V power supply, and a power source via the USB Type-C (USB-C) connector.

Communication options such as USB-UART, USB HOST/DEVICE, CAN (on the MCU card, if supported), and Ethernet is also included. In addition, it also has the well-established mikroBUS™ standard, a standardized socket for the MCU card (SiBRAIN standard), and two display options for the TFT board line of products and character-based LCD. Fusion for ARM v8 is an integral part of the Mikroe ecosystem for rapid development. Natively supported by Mikroe software tools, it covers many aspects of prototyping and development thanks to a considerable number of different Click boards™ (over a thousand boards), the number of which is growing every day.

Microcontroller Overview

MCU Card / MCU

Type

8th Generation

Architecture

ARM Cortex-M4

MCU Memory (KB)

256

Silicon Vendor

STMicroelectronics

Pin count

RAM (Bytes)

49152

Used MCU Pins

mikroBUS™ mapper

Analog Output

PA0

RST

Gain Mode Control Signal 1

PB9

SCK

MISO

MOSI

Power Supply

3.3V

Ground

GND

Gain Mode Control Signal 2

PB10

PWM

INT

I2C Clock

PB6

SCL

I2C Data

PB7

SDA

Power Supply

Ground

GND

Take a closer look

Click board™ Schematic

Step by step

Project assembly

Fusion for PIC v8 front image hardware assembly

Start by selecting your development board and Click board™. Begin with the Fusion for ARM v8 as your development board.

NECTO Output Selection Step Image hardware assembly

In the advanced settings, pay special attention to the Redirect standard output field. By default, it is set to Application output as the method of displaying final results. To show results via a UART terminal, select the “UART” option in that field and click the “SAVE” button. You will be returned to the Compiler field, and now you can move on to the next step by pressing the “NEXT” button.

GNSS2 Click front image hardware assembly

SiBRAIN for PIC32MZ1024EFK144 front image hardware assembly

Board mapper by product7 hardware assembly

NECTO Compiler Selection Step Image hardware assembly

Track your results in real time

Application Output

1. Application Output - In Debug mode, the 'Application Output' window enables real-time data monitoring, offering direct insight into execution results. Ensure proper data display by configuring the environment correctly using the provided tutorial.

2. UART Terminal - Use the UART Terminal to monitor data transmission via a USB to UART converter, allowing direct communication between the Click board™ and your development system. Configure the baud rate and other serial settings according to your project's requirements to ensure proper functionality. For step-by-step setup instructions, refer to the provided tutorial.

3. Plot Output - The Plot feature offers a powerful way to visualize real-time sensor data, enabling trend analysis, debugging, and comparison of multiple data points. To set it up correctly, follow the provided tutorial, which includes a step-by-step example of using the Plot feature to display Click board™ readings. To use the Plot feature in your code, use the function: plot(*insert_graph_name*, variable_name);. This is a general format, and it is up to the user to replace 'insert_graph_name' with the actual graph name and 'variable_name' with the parameter to be displayed.

Software Support

Library Description

This library contains API for Ambient 18 Click driver.

Key functions:

ambient18_set_gain_mode - This function sets the gain mode
ambient18_read_voltage - This function reads raw ADC value and converts it to proportional voltage level
ambient18_voltage_to_lux - This function calculates illuminance (lux) based on the voltage input

Open Source

Code example

The complete application code and a ready-to-use project are available through the NECTO Studio Package Manager for direct installation in the NECTO Studio. The application code can also be found on the MIKROE GitHub account.

/*!
 * @file main.c
 * @brief Ambient 18 Click Example.
 *
 * # Description
 * This example demonstrates the use of Ambient 18 Click board by measuring and displaying
 * the illuminance value in Lux.
 *
 * The demo application is composed of two sections :
 *
 * ## Application Init
 * Initializes the driver and sets the gain mode to M-Gain which can detect 
 * the illuminance of up to 1000 lux.
 *
 * ## Application Task
 * Reads the ADC voltage and then calculates the illuminance from it.
 * The calculated value of illuminance in lux is being displayed on the USB UART 
 * approximately once per second.
 *
 * @author Stefan Filipovic
 *
 */

#include "board.h"
#include "log.h"
#include "ambient18.h"

static ambient18_t ambient18;   /**< Ambient 18 Click driver object. */
static log_t logger;    /**< Logger object. */

void application_init ( void )
{
    log_cfg_t log_cfg;  /**< Logger config object. */
    ambient18_cfg_t ambient18_cfg;  /**< Click config object. */

    /** 
     * Logger initialization.
     * Default baud rate: 115200
     * Default log level: LOG_LEVEL_DEBUG
     * @note If USB_UART_RX and USB_UART_TX 
     * are defined as HAL_PIN_NC, you will 
     * need to define them manually for log to work. 
     * See @b LOG_MAP_USB_UART macro definition for detailed explanation.
     */
    LOG_MAP_USB_UART( log_cfg );
    log_init( &logger, &log_cfg );
    log_info( &logger, " Application Init " );

    // Click initialization.
    ambient18_cfg_setup( &ambient18_cfg );
    AMBIENT18_MAP_MIKROBUS( ambient18_cfg, MIKROBUS_1 );
    err_t init_flag = ambient18_init( &ambient18, &ambient18_cfg );
    if ( ( ADC_ERROR == init_flag ) || ( I2C_MASTER_ERROR == init_flag ) )
    {
        log_error( &logger, " Communication init." );
        for ( ; ; );
    }
    
    ambient18_set_gain_mode ( &ambient18, AMBIENT18_MODE_M_GAIN );
    log_printf( &logger, " M-Gain mode selected.\r\n Up to 1000 lux can be measured.\r\n" );
    
    log_info( &logger, " Application Task " );
}

void application_task ( void ) 
{
    float voltage = 0;
    if ( AMBIENT18_OK == ambient18_read_voltage ( &ambient18, &voltage ) ) 
    {
        log_printf( &logger, " Illuminance : %ld Lux\r\n\n", ambient18_voltage_to_lux( &ambient18, voltage ) );
        Delay_ms ( 1000 );
    }
}

int main ( void ) 
{
    /* Do not remove this line or clock might not be set correctly. */
    #ifdef PREINIT_SUPPORTED
    preinit();
    #endif
    
    application_init( );
    
    for ( ; ; ) 
    {
        application_task( );
    }

    return 0;
}

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